Modeling and Control of a Soft Robotic Arm Based on a Fractional Order Control Approach

Round 1

Reviewer 1 Report

This paper is concerned with fractional order control of a soft robotic arm. But, to the knowledge of the reviewer, the contribution of the paper is not sufficient to be accepted and published in this journal for the following reasons but not limited to:

1) In this paper, the design of the fractional order controller is not described in detail, which is the major probelm to be solved.

2) The results are not compared with the state-of-the-art literature.

3) The writing of the English is not friendable, there are many grammar errors in the presentation.

4）The novelty of the manuscript is not clear, and the application of fractional modeling and control approach is not the contribution of a new robotic problem.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Manuscript ID: fractalfract-2014184

Journal: Fractal and Fractional

Special Issue: Fractional Order Control Techniques for Robots

Title: “Modeling and control of a soft robotic arm based on a fractional

order control approach”

Abstract:

“Controlling soft robots is a significant challenge due to the nonlinear elastic nature of the soft materials that conform their structure. This paper studies the identification and control problems of a two-degree-of-freedom tendon-actuated soft robotic arm. A decoupled identification approach is presented, and later a fractional order control strategy is proposed and tested experimentally, in comparison with PI solutions. The simulation and experimental results show the goodness of the modeling and control approaches discussed.”

Reviewer comments:

The paper presents the identification of a two-degree-of-freedom tendon-actuated soft robotic arm by means of two transfer functions, together with the tuning of PI and FOPI controllers. Two experiments have been carried out and four controllers have been tuned, two for each experiment (one PI and one FOPI). Results show good performance of both controllers in the first experiment. Nevertheless, when increasing the speed requirement in the second experiment, the performance of the PI controller with a load in the tip is not as good as the FOPI controller.

The paper is very well written and the area is really interesting. Some major and minor comments are indicated below.

Major comments:

1.    In section 4.1., two transfer functions named  and  are said to be identified from real data, but they have not been defined yet. The reviewer suggests defining the expressions of these transfer functions before mentioning them, maybe in section 3.

Minor comments:

1.      The reviewer suggests to define the subindex of equation (17) as FOPI, in order to be consistent with the explanation given above the equation and with the subindex of equations (20) and (21).

2.      Revise if a gap should be left between the numbers and units when defining parameters. Also, revise if the units should be written in italics or not.

3.      The reviewer suggests revising the whole paper in order to correct some typos, such as:

a.      Line 17: “major” is repeated twice.

b.      Line 93: method-ology.

c.      Line 125: “independent”, the “n” is missing.

d.      Line 133: “angel” should be “angle”.

e.    Line 145: .

f.       Line 151: “Equations 8, 7 and 9” should be indicated in order.

g.      Line 188: consid-ering.

h.      Line 236: “met” or “meet”?

i.       Line 271: “were found” should be deleted.

j.       Line 290: “show” should be “shown”.

k.      Line 317: corre-sponding.

l.       Line 336: mechan-ical.

m.    Line 373: “when a loads are connected”, “loads” and “are” should be in singular.

Comments for author File: Comments.pdf

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The manuscript has been modified and now it can be considerted to be published in this journal.